In numerous vehicles, such as motorcycles, which have handlebars for steering, the speed of the vehicle's engine is controlled by a rotatable throttle-pipe handle mounted on an end of one of the handlebars. The rotatable throttle-pipe handle is mechanically coupled via, e.g., one or more throttle cables, to the throttle linkage of the vehicle's carburetor. Thus, by rotating the throttle-pipe handle, the engine speed and, therefore, the speed of the vehicle, may be controlled.
For safety purposes, the throttle-controller is typically resiliently biased, e.g., using a return spring, to return the throttle-pipe handle to an engine idle position when an operator's grasp on the throttle-pipe handle is released. Thus, to maintain a constant speed, an operator of the vehicle must hold the throttle-pipe handle firmly at a desired rotational position. On a long motorcycle trip, for example, this can become very fatiguing. Holding the throttle-pipe handle in a desired position for a long duration can be dangerous if the prolonged exertion required to maintain the throttle-pipe handle in a desired position causes the operator's hand and/or arm to fall asleep. Avid motorcyclists may experience medical problems, such as Carpal Tunnel Syndrome, which may be caused by the repeated and prolonged stress, lack of circulation, numbness, and fatigue to the hand which results from extended periods with the hand tightly grasped around the throttle-pipe handle to maintain the handle in a desired position.
Numerous devices and methods have been developed with the intended purpose of allowing a motorcycle operator to establish a desired motorcycle cruising speed without requiring a constant forceful turning of the throttle-pipe handle. Such devices may be referred to generally as motorcycle cruise control devices. Some of the most simple motorcycle cruise control devices employ springs which bias the throttle-pipe handle toward the "on" position, to thereby counteract, or partially counteract, the bias of the return spring, which attempts to return the throttle pipe handle to the idle position. Such devices attempt either to reduce the amount of effort required to advance the throttle-pipe handle, or to balance the rotational forces applied to the throttle-pipe handle so that the throttle-pipe handle will stay in a given position. If such a device simply reduces the amount of effort required to advance the throttle pipe handle, it is only a partial solution, since the throttle-pipe handle must still be grasped, turned, and held in position continuously to maintain a desired engine speed. If the device is designed to balance the forces applied to the throttle-pipe handle, the throttle-pipe handle will not automatically return to the idle position when the handle is released. Such a device requires that the throttle pipe handle be returned manually to the idle position. In a rapidly developing emergency situation, failure to return the throttle pipe handle to the idle position rapidly and automatically can be hazardous.
Other known cruise control devices employ a split-ring retainer mounted around the outer circumference of the throttle-pipe handle and fixed to the handle bar. A manually actuated cam lever is provided on the split-ring to clamp the ring around the throttle pipe handle, to prevent rotation thereof, when the throttle-pipe handle has been rotated to a desired position. By thus locking the throttle-pipe handle into a desired position on the handlebar, a desired engine speed can be maintained. The split-ring retainer is released manually, via manual actuation of the cam lever, to allow free rotation of the throttle-pipe handle. Thus, in an emergency situation, the cam lever must be manually actuated to allow the throttle-pipe handle to return automatically to the idle position by operation of the return spring. The requirement for manual release of such cruise control devices can be hazardous in a rapidly developing emergency situation. Examples of cruise control devices employing split-ring retainers are illustrated and described in U.S. Pat. Nos. 3,982,446, 4,137,793, 4,256,197, U.S. Pat. No. Des. 267,085 and U.S. Pat. No. Des. 273,101.
A more advanced system for maintaining a motorcycle throttle-pipe handle in a desired cruising position is described in U.S. Pat. No. 4,286,700. This patent describes a mechanically actuated locking arm mounted to the rotatable throttle-pipe handle and a cog fixedly mounted to the motorcycle handlebar. The locking arm may be mechanically actuated to engage the cog to prevent throttle rotation when the throttle-pipe handle is turned to a desired position. The locking arm may be disengaged from the cog either manually or automatically when the motorcycle's brakes are engaged. Automatic release of the locking arm from the cog is achieved using a solenoid actuator electrically connected for operation with the motorcycle brake system or brake lights. Although this system does provide for automatic release of the throttle-pipe handle to the idle position in an emergency situation, when the motorcycle brake is actuated, the system is complex, bulky, and has several other drawbacks. For example, the throttle-pipe handle may only be fixed in one of a discreet and limited number of positions defined by the cog teeth. Thus, such a system does not allow fixing of the throttle-pipe handle in any desired position. Furthermore, once the locking arm is engaged with the cog, the cruise control system must be disengaged, to remove the locking arm from the cog, in order for the cruising speed to be adjusted (either slowed down or sped up). Thus, such a system does not allow adjustment of the motorcycle cruising speed without disengaging and then re-engaging the cruise control mechanism.
Much more advanced and complicated motorcycle cruise control systems have also been developed. Such systems may typically employ, for example, microprocessor controlled systems for controlling the vehicle's engine speed to maintain a desired vehicle speed. Such systems are comparable in complexity to cruise control systems employed in automobiles, for example. Although such systems are effective, they are relatively very complex and expensive, and are therefore only suitable for the largest and most expensive motorcycles. Examples of such complicated cruise control systems are described in U.S. Pat. Nos. 4,580,537, 4,587,937, 4,966,247 and 4,969,531.